Our mission is to increase testing for infectious diseases by offering fast and convenient COVID-19 testing and onsite HIV and HCV testing to patients, businesses, and healthcare facilities.
Now that we are over a year into the COVID-19 pandemic, we are well aware of the steps we need to take to effectively control the spread of the virus: prevention measures like wearing masks, washing hands, and distancing; widespread COVID-19 testing with quick turnaround times; and contact tracing for people who test positive to help stop transmission of the virus. These are the best actions that we can take while waiting for widespread vaccination.
Does the vaccine protect everyone against COVID-19?
The short answer is, no. While getting vaccinated is one of the best steps we can take to prevent the disease, not everyone who gets vaccinated will remain disease free. On April 14th, 2021, the CDC reported that more than 75 million Americans had been vaccinated against COVID-19 since December 14th, 2020. During this time, the CDC also received 5,814 reports of vaccine "breakthrough" infections from 43 U.S. states and territories. Breakthrough cases are COVID-19 infections occurring in people who have been vaccinated. In this same report from the CDC, it was reported that while there is some evidence that vaccination may make illness less severe, there will be a small percentage of people who are fully vaccinated who still get sick, are hospitalized, or will die from COVID-19.
How long does the vaccine last?
Although Americans have been fighting COVID-19 for over a year, vaccines for the disease have only recently been granted emergency use authorization, so experts have not had enough time to observe the long-term effects of the vaccines. On March 29th, 2021, Lindsey Bever reported in the Seattle Times that, "...experts do know that vaccine-induced immunity should last a minimum of about three months," which is not to say that their effectiveness will automatically wear off after 90 days. Pfizer's ongoing trial indicates that the company's two-dose vaccine remains highly effective for at least six months, and likely longer. Moderna's vaccine also still had notable levels of antibodies six months after the second required shot. As time goes on and with further studies, we will be able to determine the length of effectiveness of the vaccines.
So, which tests to use? There are COVID-19 tests that diagnose current infection and tests that show whether you previously had SARS-CoV-2, the virus that causes COVID-19.
The FDA has granted emergency use authorization (EUA) for hundreds of COVID-19 diagnostic tests. This allows test manufacturers to market tests without receiving formal FDA approval because there is a public health emergency.
Because this novel coronavirus is novel (a new disease), information about available tests is incomplete and testing options continue to change. Tests vary in terms of accuracy, cost, recommended use for people of various ages, and convenience. The following information, taken from the Harvard Health Publishing Coronavirus Resource Center, provides a breakdown of the types of COVID-19 tests that are available. For more detailed information on individual tests, check the FDA’s updated list of authorized tests, which has links to the test makers’ websites.
Diagnostic tests for current infection
If you want to know if you have the virus, there are two types of tests: molecular tests and antigen tests.
Molecular tests (also called PCR tests, viral RNA tests, nucleic acid tests)
How is it done? Nasal swabs, throat swabs, and tests of saliva or other bodily fluids.
Where can you get this test? At a hospital, in a medical office, or a private laboratory. Prevention Healthcare Services is a laboratory licensed by the New York State Department of Health Clinical Laboratory Evaluation Program. You may be asked to come into an office, but most commonly the test is done while you wait in your car. We test our patients here while they stay in their car, and onsite at other locations.
What does the test look for? Molecular tests look for genetic material that comes only from the virus.
How long does it take to get results? It depends on lab capacity. Results may be ready within hours, but often take at least a day or two. Much longer turnaround times are reported in many places. The molecular test that we use can provide test results to our patients in an hour or less.
What about accuracy? The rate of false negatives is the percentage of tests that say you don’t have the virus when you actually do have the virus — varies depending on how long infection has been present: in one study, the false-negative rate was 20% when testing was performed five days after symptoms began, but much higher (up to 100%) earlier in infection. As the number of tests have increased, we have seen a slight decline in the false negative rates. The molecular test that we use has a false negative rate of approximately 6%, with a 94% positive percent agreement (PPA).
The false positive rate — that is, how often the test says you have the virus when you do not — should be close to zero. Most false-positive results are thought to be due to lab contamination or other problems with how the lab has performed the test, not limitations of the test itself. The molecular test that we use has a false positive rate of 2%, with 98% negative percent agreement (NPA).
A molecular test using a nasal swab is usually the best option, because it will have fewer false negative results than other diagnostic tests or samples from throat swabs or saliva. People who are in the hospital, though, may have other types of samples taken.
How is it done? A nasal or throat swab.
Where can you get these tests? At a hospital, a doctor’s office, or a licensed laboratory.
What does the test look for? This test identifies protein fragments (antigens) from the virus.
How long does it take to get results? The technology involved is similar to a pregnancy test or a rapid strep test, with results available in minutes.
What about accuracy? False negative results tend to occur more often with antigen tests than with molecular tests. Antigen tests are not favored by the FDA as a single test for active infection. Positive results from an antigen test should be confirmed with a molecular test. As with the molecular test, the false positive rate of antigen testing should be close to zero.
Tests for past infection
An antibody test can show if you have previously been infected with the COVID-19 virus.
Antibody tests (also called serologic testing)
How is it done? A sample of blood is taken.
Where can you get these tests? At a doctor’s office, blood testing lab, or hospital.
What does the test look for? These blood tests identify antibodies that the body’s immune system has produced in response to the infection. While a serologic test cannot tell you if you have an infection now, it can accurately identify past infection.
How long does it take to get results? Results are generally available within a few days.
What about accuracy? Having an antibody test too early can lead to false negative results. That is because it takes a week or two after infection for your immune system to produce antibodies. The reported rate of false negatives is 20%. However, the range of false negatives is from 0% to 30%, depending on the study and when in the course of infection, the test is performed.
Research suggests antibody levels may wane over just a few months. While a positive antibody test proves you have been exposed to the virus, it is not yet known whether such results indicate a lack of contagiousness or long-lasting, protective immunity.
For up-to-date information, with answers to most questions related to COVID-19, please see one of our many COVID-19 resources, Harvard Health Publishing Coronavirus Resource Center.